1. Field of the Invention
The present invention relates to an automatic document feeder employed in office appliances such as a photocopy machine, scanner, facsimile and multi-function office machine. More particularly, the present invention relates to a method for creating uniform intervals between document sheets being fed.
2. Description of the Related Art
Automatic document feeders used with multi-function office machines typically comprise a paper feeding tray where a document, often having a plurality of paper sheets, is set, a paper feeding roller for separately transferring the document on the paper feeding tray sheet by sheet, an arranging roller for arranging a front end of the document being transferred by the paper feeding roller, a scanning roller for taking the document being transferred by the arranging roller to an image reading sensor, a gate roller for transferring the read document toward a paper discharging part, and a paper discharging roller.
The paper feeding tray has a document sensor for detecting whether the document is set thereon, and the arranging roller has an arranging sensor for detecting the transfer of the document at a front portion thereof. Also, the scanning roller has a scanning sensor at a rear portion thereof for detecting an entering point of the document toward the image reading sensor, and the gate roller has a gate sensor at a rear portion thereof for detecting the transfer of the document.
In the example wherein a duplex scanning mode is provided, the automatic document feeder further comprises a duplex document path, a duplex gate for guiding the document to the duplex document path, a document entering sensor for detecting the document entering the duplex document path, and a duplex document transfer roller.
In the general automatic document feeder as described above, as a paper feeding clutch is turned on, the paper feeding roller is rotated, thereby feeding the plurality of paper sheets of a document set on the paper feeding tray one by one. The front end of the document transferred by the paper feeding roller is arranged by the arranging roller. As an arranging clutch is turned on, the arranging roller is rotated and therefore, the document is continuously transferred. At this time, the arranging sensor is in an on state, while the paper feeding clutch is in an off state. When the arranging sensor is turned off as the document passes therethrough, the paper feeding clutch is turned on again, thereby rotating the paper feeding roller to feed the next sheet of the document.
To summarize, in the conventional automatic document feeder, a next sheet is fed after a previous sheet is completely passed through the arranging sensor, such that an interval between the sheets is constantly maintained.
However, according to such conventional paper feeding methods, even when a sheet is fed together with a previous sheet by error, the following sheet is continuously fed because the arranging sensor is turned off. Therefore, the intervals between sheets may be shortened and this may cause malfunctions of the sensors or paper jams.
In addition, such variation of the intervals between the sheets deteriorates the reliability of the production of machines, such as the photocopy machine or the multi-function office machine. For example, the number of scanned sheets per minute may differ from a preset value.
Accordingly, a need exists for a system and method for controlling the intervals between sheets such that malfunctions of the sensors and paper jams can be minimized.